394 



PROCEEDINGS OF THE ACADEMY OF 



[1897. 



to the head and thorax in length, the flagellum has twenty-one arti- 

 cles. The basal segment of the peduncle is short, reaching but a 

 little beyond the front ; the second segment is as broad as long ; 

 the third segment is about once and a half as long as broad ; the 

 fourth is a little more than twice the breadth ; the fifth is nearly as 

 long as the third and fourth together. The antennulse extend a lit- 

 tle beyond the base of the fourth segment of the antenna?. 



The thorax is widest at the fourth segment. From the sides of 

 the fourth segment the outline curves around to the eye. Poste- 

 riorly from the fourth segment the outline is straight to the distal 

 third of the abdomen. The second, third and fourth segments are 

 longest. There are no spines or tubercles anywhere and the rugos- 

 ities so common to the species of the genus are barely indicated. 



The abdomen is very little longer than its breadth at the base. 

 It tapers gradually for the first two-thirds of its length where it be- 

 gins to taper more rapidly to a broad emarginate extremity. 



The feet are sparsely set with coarse hair. The valves of the 

 operculum are diagonally crossed by a curved line. 



The specimen is clouded with dark patches made up of small 

 black spots. 



This species can be distinguished from any other yet described by 

 its broadly emarginate abdomen. 



Length 17 mm., width 7 mm. (No. 20,504, U. S. N. M.). 



Synidotea nebulosa, new species. Fig. 5. 

 The front of the head is exca- 

 vated ; between the median notch 

 and the antero-lateral margin the 

 outline is emarginate ; between the 

 margin and the eyes the protuber- 

 ances are but little elevated ; the 

 cross areolation is smooth ; the lat- 

 eral areolations are separated by 

 an extension of the cross ; this ex- 

 tension is itself slightly divided by 

 a slightly impressed line. The de- 

 pression in front of the postce- 

 phalic lobe is deep. The sides of 

 the head extend to the vertical 

 line of the eyes, cutting off the vi- 

 sion from objects directly below. 

 The antennae are about 6 mm. in Benedict. 



Fig. 5. Synidotea nebulosa 



